Ground-engaging tools such as ripper teeth, earthmoving buckets, and cutting edges for various blades are often subject to a rapid rate of wear due to continual contact of the tool with rock, sand, and earth. Upon experiencing a preselected degree of wear, the worn tool is typically removed from the implement and a new tool installed, or alternately the tool is rebuilt by adding hardfacing weld material to the critically worn regions thereof. Because this repetitive and expensive maintenance is required, the industry has continued to search for and develop tools having the lowest possible hourly cost and/or an extended service life to minimize loss of machine downtime.
One approach to these problems is to utilize carbide tool materials containing such elements as tungsten, cobalt, and tantalum for increased wear-resistance. Tungsten carbide tools, for example, have been widely adopted because of their wear-resistance for metal cutting and manufacturing purposes. Unfortunately, these elements are either strategic or scarce, so that the carbide materials are price sensitive.
Another recently developed tool material competing with cobalt-bonded tungsten carbide includes the carbides of titanium and chromium with a nickel base alloy as a binder material. While such a composite material family also offers several advantageous properties, the binder or matrix phase thereof has insufficient ductility so that it is not desirable for use with tools that are subjected to frequent shocks. Representative of this category is U.S. Pat. No. 3,258,817 issued July 5, 1966 to W. D. Smiley.
Another particularly promising family of materials is represented by cemented borides. Chromium borides, for example, have been under development for some time as is indicated by U.S. Pat. No. 1,493,191 which issued May 6, 1924 to A. G. DeGolyer, and more recently by U.S. Pat. No. 3,970,445 which issued July 20, 1976 to P. L. Gale, et al. Other boride materials have been considered as is evidenced by: U.S. Pat. No. 3,937,619 which issued Feb. 10, 1976 to E. V. Clougherty on use of titanium, zirconium, and hafnium with boron; U.S. Pat. No. 3,954,419 which issued May 4, 1976 to L. P. Kaufman on titanium diboride mining tools; and U.S. Pat. No. 3,999,952 which issued Dec. 28, 1976 to Y. Kondo, et al on a sintered alloy of multiple boride containing iron. Moreover, boride compounds are discussed in the following references: article by R. Steinitz and I. Binder entitled "New Ternary Boride Compounds" in the February 1953 issue of Powder Metallurgy Bulletin; paper by A. G. Metcalfe entitled "Cemented Borides for Tool Materials" and presented at the Mar. 19-23, 1956 meeting of the American Society of Tool Engineers; and an article by P. T. Kolomytsev and N. V. Moskaleva entitled "Phase Composition and Some Properties of Alloys of the System Molybdenum-Nickel-Boron" and published in Poroshkovaya Metallurgiya, No. 8 (44), pages 86-92, August 1966. These borides contain strategic, price-sensitive elements such as nickel and chromium and/or do not necessarily offer the best wear resistance.
The present invention is directed to overcoming one or more of the problems as set forth above.